U.S. patent number 11,209,045 [Application Number 16/802,715] was granted by the patent office on 2021-12-28 for dual land journal bearings for a compound planetary system.
This patent grant is currently assigned to PRATT & WHITNEY CANADA CORP.. The grantee listed for this patent is PRATT & WHITNEY CANADA CORP.. Invention is credited to Louis Brillon, Martin Poulin.
United States Patent |
11,209,045 |
Brillon , et al. |
December 28, 2021 |
Dual land journal bearings for a compound planetary system
Abstract
A journal bearing assembly for rotatably supporting at least one
gear, comprising a pin and a journal shaft. The journal shaft
includes an inner cavity receiving the pin and an outer surface
including a plurality of contact surfaces supporting the at least
one gear and at least one annular groove separating adjacent
contact surfaces. The pin is configured to support the journal
shaft at a support position in the inner cavity.
Inventors: |
Brillon; Louis (Varennes,
CA), Poulin; Martin (Mont Saint-Hilaire,
CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
PRATT & WHITNEY CANADA CORP. |
Longueuil |
N/A |
CA |
|
|
Assignee: |
PRATT & WHITNEY CANADA
CORP. (Longueuil, CA)
|
Family
ID: |
1000006019728 |
Appl.
No.: |
16/802,715 |
Filed: |
February 27, 2020 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20210254659 A1 |
Aug 19, 2021 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
62976585 |
Feb 14, 2020 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16H
57/0479 (20130101); F16C 17/02 (20130101); F16H
2057/085 (20130101); F05D 2240/54 (20130101) |
Current International
Class: |
F16C
17/02 (20060101); F16H 57/04 (20100101); F16H
57/08 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pilkington; James
Attorney, Agent or Firm: Norton Rose Fulbright Canada
LLP
Claims
The invention claimed is:
1. A journal bearing assembly for rotatably supporting at least one
gear, comprising: a pin; and a journal shaft including an inner
cavity receiving the pin and an outer surface including a plurality
of contact surfaces for supporting the at least one gear and at
least one annular groove separating adjacent contact surfaces;
wherein the pin has a bump configured to support the journal shaft
at a support position in the inner cavity, the support position
positioned at the longitudinal center of the journal shaft.
2. The journal bearing assembly as defined in claim 1, wherein the
at least one annular groove is positioned at the longitudinal
center of the journal shaft.
3. The journal bearing assembly as defined in claim 1, wherein the
at least one annular groove includes a rectangular
cross-section.
4. The journal bearing assembly as defined in claim 1, wherein the
at least one annular groove includes a curved cross-section.
5. The journal bearing assembly as defined in claim 1, further
comprising a compliance gap at each distal end of the journal
shaft.
6. The journal bearing assembly as defined in claim 5, wherein each
compliance gap includes a removed section of the journal shaft.
7. The journal bearing assembly as defined in claim 5, wherein each
compliance gap includes one of a tapered or curved shape.
8. The journal bearing assembly as defined in claim 5, wherein each
compliance gap is formed adjacent the bump in the pin.
9. A gas turbine engine comprising: a gearbox having a plurality of
gears; and a journal bearing assembly including a supporting pin
and a journal shaft including an inner cavity receiving the
supporting pin and an outer surface including a plurality of
contact surfaces rotatably supporting at least one of the plurality
of gears and at least one annular groove separating adjacent
contact surfaces, wherein the pin has a bump configured to support
the journal shaft in the inner cavity at the longitudinal center of
the journal shaft.
10. The gas turbine engine as defined in claim 9, wherein the
gearbox is a compound planetary gearbox including a sun shaft, a
sun gear, a plurality of planet gears, a gear carrier and a ring
gear.
11. The gas turbine engine as defined in claim 10, wherein at least
two planet gears are supported by the journal shaft and
interconnected for concurrent rotation.
12. The gas turbine engine as defined in claim 9, wherein three
planet gears are supported by the journal shaft and interconnected
for concurrent rotation, a larger of the three planet gears is
centrally mounted on the journal shaft between the two other of the
three planet gears.
13. The gas turbine engine as defined in claim 9, further
comprising a sleeve disposed radially outwardly to the journal
shaft, the sleeve forming an outer peripheral surface between the
journal shaft and the at least one supported gear.
14. The gas turbine engine as defined in claim 9, wherein the at
least one annular groove is positioned at the longitudinal center
of the journal shaft.
15. The gas turbine engine as defined in claim 9, wherein the at
least one annular groove includes a rectangular cross-section.
16. The gas turbine engine as defined in claim 9, wherein the at
least one annular groove includes a curved cross-section.
17. A method for rotatably supporting at least one gear in a
gearbox, comprising: mounting the at least one gear onto a journal
bearing assembly including a journal shaft and a pin inserted into
an inner cavity of the journal shaft, the pin having a bump
supporting the journal shaft in the inner cavity at the
longitudinal center of the journal shaft, the at least one gear
rotatable about a longitudinal axis of the journal bearing
assembly; and positioning at least two contact surfaces on an
outside surface of the journal shaft to rotatably support the at
least one gear, the at least two contact surfaces separated by an
annular groove.
18. The method as defined by claim 17, further comprising fitting
an annular sleeve between the journal shaft and the at least one
gear to be supported.
Description
TECHNICAL FIELD
The present disclosure relates generally to mounting devices for
rotating assemblies of gas turbine engines, and more particularly
to journal bearings for such engines.
BACKGROUND OF THE ART
Turbine engines typically include a number of rotating components
or parts mounted together via mounting devices providing suitable
support and allowing axial and/or rotational movement between such
components. Those mounting devices may be journal bearings. Long
journal bearings with high length-to-diameter ratios typically
require various compliance features such as compliance wings or the
like to reduce local stiffness and decrease the journal pressure.
The large radial space taken by these compliance features may
reduce the possible diameter of the pin passing through the journal
bearing, which may thus be subjected to undesirable higher bending
deformations under load.
SUMMARY
In one aspect, there is provided a journal bearing assembly for
rotatably supporting at least one gear, comprising a pin, and a
journal shaft including an inner cavity receiving the pin and an
outer surface including a plurality of contact surfaces supporting
the at least one gear and at least one annular groove separating
adjacent contact surfaces, wherein the pin is configured to support
the journal shaft at a support position in the inner cavity.
In another aspect, there is provided a gas turbine engine
comprising a gearbox having a plurality of gears, and a journal
bearing assembly including a supporting pin and a journal shaft
including an inner cavity receiving the supporting pin and an outer
surface including a plurality of contact surfaces rotatably
supporting at least one of the plurality of gears and at least one
annular groove separating adjacent contact surfaces.
In a further aspect, there is provided a method for rotatably
supporting at least one gear in a gearbox, comprising mounting the
at least one gear onto a journal bearing assembly including a
journal shaft and a pin insertable into an inner cavity of the
journal shaft, and positioning at least two contact surfaces on an
outside surface of the journal shaft to rotatably support the at
least one gear, the at least two contact surfaces separated by an
annular groove.
DESCRIPTION OF THE DRAWINGS
Reference is now made to the accompanying figures in which:
FIG. 1 is a schematic sectional view of a gas turbine engine with a
bearing assembly of the present disclosure;
FIG. 2 is a schematic cutaway perspective view of a gear assembly
as used in the engine of FIG. 1 and showing a journal bearing
assembly, according to an embodiment of the present disclosure;
FIG. 3 is a longitudinal section perspective view of an embodiment
of a journal bearing assembly according to the present
disclosure;
FIG. 4 is a longitudinal section perspective view of another
embodiment of a journal bearing assembly according to the present
disclosure;
FIG. 5 is a longitudinal section perspective view of another
embodiment of a journal bearing assembly according to the present
disclosure;
FIG. 6 is a longitudinal section perspective view of another
embodiment of a journal bearing assembly according to the present
disclosure; and
FIG. 7 is a longitudinal section perspective view of another
embodiment of a journal bearing assembly according to the present
disclosure.
DETAILED DESCRIPTION
FIG. 1 illustrates a gas turbine engine 10 of a type preferably
provided for use in subsonic flight and configured for driving a
load 12, such as, but not limited to, a propeller or a helicopter
rotor or rotorcraft rotor. Depending on the intended use, the
engine 10 may be any suitable aircraft engine, and may be
configured as a turboprop engine or a turboshaft engine. The gas
turbine engine 10 generally comprises in serial flow communication
a compressor section 14 for pressurizing the air, a combustor 16 in
which the compressed air is mixed with fuel and ignited for
generating an annular stream of hot combustion gases, and a turbine
section 18 for extracting energy from the combustion gases. Also
shown is a central longitudinal axis 11 of the engine 10. Even
though the present description specifically refer to a turboprop
engine as an example, it is understood that aspects of the present
disclosure may be equally applicable to other types of combustion
engines in general, and other types of gas turbine engines in
particular, including but not limited to turboshaft or turbofan
engines, auxiliary power units (APU), and the like.
The gas turbine engine 10 also includes rotating parts or
assemblies, such as gear assemblies 19 (e.g., epicycle reduction
systems, planetary/reduction gearboxes (RGB), or other types of
rotating assemblies) with rotating components mounted thereto using
mounting devices allowing rotational and/or axial movement. In the
embodiment shown, the gear assembly 19 is mounted at the front end
of the engine 10, though it may be at other locations in the engine
10. An example of a gear assembly 19 as used in the engine 10 is
shown in FIG. 2. In the depicted embodiment, the gear assembly 19
is part of a compound epicycle reduction system, also known as
epicyclic gear train, epicyclic gearbox, planetary gearbox, etc. As
a contemplated embodiment among others, an input torque through a
sun shaft 20 is rotatably outputted through a sun gear 21 as an
output torque through gear carriers 22 via a plurality of planet
gears 24 rotatably connected to the gear carriers 22 and ring gears
26.
The gear assembly 19 shown in FIG. 2 includes one or more mounting
devices such as a journal bearing assembly 28. As shown in FIG. 3,
the journal bearing assembly includes a journal shaft 30 (also
referred to as a journal or a shaft), a pin 32, and an optional
sleeve 34. The journal bearing assembly 28 may be used for
interfacing a rotating part to a structure. In the example shown,
the rotating part is one or more gears such as planet gears 24,
although other arrangements are possible. The gear may be an
epicycle gear of epicyclic reduction system, mounted on the journal
bearing assembly 28 which is supported at both ends between two
axially spaced supports forming at least part of the structure of
the epicyclic gear system, the structure being for instance a
carrier 22. In an embodiment, there are a plurality of planet gears
24 (illustratively three planets 24a, 24b 24c) on the carrier 22,
the planet gears 24 being interconnected for concurrent rotation.
The supports may be annular blocks (not shown) supporting the pin
32 at its opposed ends. The pin 32 may be hollow with a pin inner
cavity 36 (as shown in FIG. 3) and may be optionally closed at one
end via a fastener such as a bolt and a washer (not shown). A
lubricating fluid film, such as an oil film, may be received
between rotating components of the journal bearing assembly 28 to
facilitate rotation of said components relative to one another. In
addition, the pin inner cavity 36 may include various (not shown)
inlet and outlet passages for oil to flow through.
Although not shown, other types of bearings may be used, such as
roller bearings, ball bearings or any other suitable types of
bearings. The journal bearing assembly 28 may or may not include
the sleeve 34 disposed radially outwardly to the journal shaft 30
relative to a longitudinal axis A of the journal bearing assembly
28. Such sleeve 34 may be used to form an outer peripheral surface
of the journal bearing assembly 28, upon which the planet gears 24
are mounted in the illustrated embodiment. Otherwise, an outer
surface 38 of the journal shaft 30 may contact directly the
rotating part it supports, e.g., the planet gears 24 in the
illustrated embodiment.
Referring to FIG. 3, an embodiment of a journal bearing assembly 28
is shown. The journal shaft 30 may be a monolithic piece. While
journal shaft 30 is shown to be cylindrical, other shapes are
possible such as frusto-conical, and the journal shaft may have
various surface features such as grooves, slots and channels. The
journal shaft 30 extends along the longitudinal axis A, which is
the rotation axis of the rotating part, illustratively the three
planet gears 24a, 24b, 24c. The journal shaft's outer surface 38 is
configured for interfacing and supporting the rotating part either
directly or via the optional sleeve 34. A pin-receiving inner
cavity 40 (a.k.a., throughhole) extends along the longitudinal axis
A and defines a pin-engaging surface 42. The pin-receiving cavity
40 may thus receive the pin 32 of the gear assembly 19 when mounted
within such assembly 19. A support position 44 at a given location
on the pin-engaging surface 42, illustratively towards the center
of the journal shaft 30, allows the pin 32 to support the journal
shaft 30. This support position 44 assists in providing local
compliance between the rotating part and the journal shaft 30.
Depending on the configuration, the journal bearing assembly 28 may
have its journal shaft 30 fixed to the pin 32, such that the sleeve
34 (if present) or the rotating part rotates about the pin 32 and
the journal shaft 30. If present, the sleeve 34 concurrently
rotates with the rotating part fixed thereon. In another
embodiment, the journal bearing assembly 28 may have its journal
shaft 30 rotatably engaged with the rotating part it supports, such
that the journal shaft 30 may be rotatable relative to the pin 32
and may have the rotating part mounted thereto rotatable relative
to the journal shaft 30, for instance with the sleeve 34 fixed to
the rotating part or to the journal shaft 30.
In the embodiment shown in FIG. 3, the outer surface 38 of the
journal shaft 30 includes a plurality of contact surfaces or
journal lands 46 (illustratively two contact surfaces 46) for
supporting the rotating part, illustratively the three planet gears
24a, 24b, 24c. An annular groove 48 in the journal shaft 30
separates adjacent contact surfaces 46. While the embodiment of
FIG. 3 shows a single annular groove 48 separating two adjacent
contact surfaces 46, other arrangements are possible, such as two
annular grooves 48 interspersed between three contact surfaces 46.
In the shown embodiment, the annular groove 48 is located towards
the center of the journal shaft 30 where the journal shaft 30 is
typically subjected to less pressure than the rest of the shaft 30,
while the now shorter contact surfaces 46 are positioned beneath
the areas of increased load. By separating the typically single
continuous contact surface into two or more distinct contact
surfaces 46, such as ones separated by one or more annular grooves,
the local applied pressures may be reduced, which may lead to less
of a bending effect along the length of the journal shaft 30. In
addition, the two or more contact surfaces 46 may lie mostly
concentrically against the rotating part such as the three planet
gears 24a, 24b, 24c or the sleeve 34.
The separate contact surfaces 46 convert a traditional journal
shaft with a long length-to-diameter ratio into two separate
segments with lower length-to-diameter ratios that, in an
embodiment, are within general journal bearing best practices. As
an example, while the use of journal bearing shafts with
length-to-diameter ratios ranging from roughly 0.5 to 1.5 has been
put forward, the use of separate contact surfaces 46 taught by the
present disclosure may allow for improved performance with longer
journal shafts having overall length-to-diameter ratios above 1.5.
Longer journal shafts 30 may often be used in compound epicyclic
gear systems in which two or more planet gears are on the journal
shaft 30. For example, in the illustrated embodiments, three planet
gears 24, illustratively a central planet gear 24a positioned
between two smaller planet gears 24b, 24c, are arranged along a
common shaft 30 and interconnected for concurrent rotation. For
example, the larger planet gear 24a may engage sun gear 21, while
the smaller planet gears 24b, 24c may engage ring gears 26. In
addition, by incorporating two or more contact surfaces 46, the
required compliance features 50 at the distal ends of the journal
shaft 30, which may be referred to as undercuts or axial
depressions, etc, may be made smaller than those in a traditional
journal shaft, which may lead to an overall thinner and hence
lighter journal shaft 30. Thus, a larger and stiffer pin 32 may be
utilized, leading to improved robustness and reliability.
In an embodiment, a compliance gap 52 at each distal end of the
journal shaft 30 may add flexibility to the journal bearing
assembly 28. Such compliance gaps 52 may be implemented in a
plurality of ways. In the embodiment shown in FIG. 3, the journal
shaft 30 includes a recess 54 at each distal end thereof to allow
for greater flexibility in case of any bending. In the embodiment
shown in FIG. 5, these recesses 54 may include curved profiles to
account for greater bending effects. Alternatively, each end of the
journal shaft 30 may include tapered profiles adding additional
compliance, as shown in FIG. 4. The surface of the recesses 54 may
be defined as having a frusto-conical geometry. In another
embodiment, the surface of the recesses 54 may be defined as having
a countersink shape.
While the embodiments of the journal bearing assembly 28 shown in
FIGS. 3-5 include a single annular groove 48 with a rectangular
cross-section, other possibilities in terms of shape and quantity
may be implemented. As shown in FIG. 6, the annular groove 48 may
include a curved cross-section. Alternatively, in the embodiment
shown in FIG. 7, the journal shaft 30 may include two annular
grooves 48, here shown to be of partially-circular cross-section,
to account for stress and oil accumulation. While the journal shaft
30 of FIG. 7 shows a transition surface 56 between the two annular
grooves 48 which does or does not make contact with the sleeve 34
(or rotating part in the absence of a sleeve) under standard
conditions, in alternate embodiments the journal shaft 30 may
include two or more annular grooves 48 that are each separated by
contact surfaces 46 for interfacing and supporting the rotating
element.
The embodiments described in this document provide non-limiting
examples of possible implementations of the present technology.
Upon review of the present disclosure, a person of ordinary skill
in the art will recognize that changes may be made to the
embodiments described herein without departing from the scope of
the present technology. Yet further modifications could be
implemented by a person of ordinary skill in the art in view of the
present disclosure, which modifications would be within the scope
of the present technology.
* * * * *